A large number of semiconductor devices are typically fabricated on a common semiconductor wafer having a diameter up to 12 inches or more and then are separated (i.e. singulated) for packaging as individual devices. These semiconductor devices, which can be integrated circuits (ICs), microprocessors, microelectromechanical systems (MEMS), microfluidic devices, sensors, etc., are conventionally singulated by saw cutting. The use of saw cutting requires a spacing (i.e. a street) between adjacent devices which are being singulated with this spacing being up to 100 microns or more wide; and this spacing limits the number of devices which can be fabricated from the semiconductor wafer. Additionally, saw cutting generates debris which can contaminate the devices or become lodged in moveable members of MEMS devices or in fluid channels of microfluidic devices. Furthermore, saw cutting must be performed along straight lines in a serial fashion one cut at a time; and this limits the shape of the devices to being square or rectangular and generally all of the same size. Saw cutting is also time since each saw cut must be carefully aligned with each street separating adjacent rows of devices to singulate the devices without damaging them. For all of the above reasons, conventional saw cutting is disadvantageous so that an advance in the art is needed to improve the singulation of devices from semiconductor wafers.
The present invention provides such an improvement in the art by providing a method for singulating one or more die from a semiconductor wafer (i.e. a semiconductor substrate) which relies on etching trenches from two opposite sides of the semiconductor wafer with a portion or all of the trench on one side of the semiconductor wafer being laterally offset from the trench on the other side of the semiconductor wafer. The trenches expose an oxide layer on the semiconductor wafer so that when the oxide layer between the trenches is etched away, the die will be singulated. The method can also provide a release fixture beneath the semiconductor wafer to receive and support the singulated die once the oxide layer is etched away between the trenches on each side of the semiconductor wafer.
The method of the present invention is compatible with standard semiconductor processes and allows all of the die on the semiconductor wafer to be singulated simultaneously in a parallel process without attachment to a handle wafer. This saves time and cost and also increases yield and performance by minimizing die handling and particulates which would otherwise occur if conventional sawing were used to singulate the die. This also eliminates adhesives which would otherwise be required to attach the die and the substrate from which the die are formed to the handle wafer, and additional cleaning steps that would be required to remove these adhesives from the singulated die.
The method of the present invention can be used to singulate die of an arbitrary shape, and can be used to form die with rounded corners.
The method of the present invention can be used with silicon-on-insulator (SOI) substrates, or bulk silicon substrates having one or more oxide and polycrystalline silicon layers deposited thereon.
The method of the present invention can also be adapted to release features within one or more MEMS devices which are formed on the die. The offset between the trenches on each side of the substrate can be predetermined so that singulation of the die by etching away the oxide layer between the trenches will occur at a time shortly after release of features within the MEMS devices.
These and other advantages of the present invention will become evident to those skilled in the art.